Oxygen absorber

ABSTRACT

An oxygen-absorbing composition containing particulate annealed electrolytically reduced iron of between about 100 mesh and 325 mesh in an amount of about up to 63% by weight, a salt such as sodium chloride in an amount by weight of about up to 3.5%, and a water-supplying component comprising activated carbon. with liquid water therein of a mesh size of between about 20 mesh and 50 mesh in an amount by weight of up to about 85% in an envelope which will resist the passage of liquid water out of the envelope but will permit flow of oxygen into the envelope at a satisfactory rate.

CROSS REFERENCE TO RELATED APPLICATION

This Application is a continuation of Ser. No. 08/328,081, filed Oct.27, 1994, now U.S. Pat. No.6,248,690, which is a continuation-in-part ofapplication Ser. No. 08/150,617, filed Nov. 10, 1993, and now abandonedwhich is a continuation-in-part of application Ser. No. 07/888,966,filed May 26, 1992, now U.S. Pat. No. 5,262,375.

BACKGROUND OF THE INVENTION

The present invention relates to an improved oxygen absorber forabsorbing oxygen primarily in ambient temperature dry environments andwhich will also function satisfactorily in in both low temperatureenvironments and in moist environments.

By way of background, particulate iron is known as an oxygen absorberbecause it readily combines with oxygen. In the past, various types ofparticulate iron have been used, including hydrogen reduced iron,electrolytically reduced iron, atomized iron, and milled pulverizediron. However, the hydrogen reduced iron, the atomized iron and themilled pulverized iron absorb oxygen relatively slowly. Theelectrolytically reduced iron absorbs oxygen faster, but at lowertemperatures at which foods are normally refrigerated it absorbs oxygenat a slower rate than desired to remove the oxygen before the initialstages of food spoilage commence. Furthermore, in dry environments it isnecessary to supply moisture for producing an electrolytic action whichis necessary for activating the oxygen-absorbing action of the iron.However, silica gel which has been used in the past for adsorbingmoisture from a moist environment cannot be used for a plurality ofreasons. The first reason is that if it contains sufficient moisture tosupply such moisture, it is not flowable and thus cannot be usedefficiently in a manufacturing process. The second reason is that if itcontains a lesser amount of moisture so that it remains flowable, itwill not give this moisture up for combining with a salt to produce anelectrolyte, and further, in a dry environment it will not have a sourceof moisture from which it can adsorb the necessary moisture foractivating oxygen absorption. Furthermore, the envelopes of certainprior oxygen-absorbing packets were deficient for use in dryenvironments in that they permitted moisture to escape from amoisture-containing oxygen-absorbing composition which diminished themoisture available for producing the required electrolytic action.

SUMMARY OF THE INVENTION

It is the primary object of the present invention to provide an improvedoxygen-absorbing composition which can supply moisture in dryenvironments for the purpose of enhancing oxygen absorption.

Another object of the present invention is to provide an improved oxygenabsorber which is flowable and which contains activated carbon with arelatively high percentage of water impregnated therein which isrequired to supply moisture for absorbing oxygen in dry environments,the flowability being required for efficient handling in themanufacturing process.

A further object of the present invention is to provide an improvedoxygen-absorbing composition which includes particulate annealedelectrolytically reduced iron and moisture-impregnated activated carbonwhich will provide good oxygen absorption in dry environments, in moistenvironments and in low temperature environments.

Yet another object of the present invention is to provide an improvedcombination of a package and an oxygen-absorbing composition which willprovide good oxygen absorption in dry environments.

A still further object of the present invention is to provide animproved combination of a package and an oxygen-absorbing compositionwhich inhibits migration of water from a moisture-carrying product inthe package and thus conserves available moisture for creating anelectrolyte for combining with iron to effect oxygen-absorption in dryenvironments. Other objects and attendant advantages of the presentinvention will readily be perceived hereafter.

The present invention relates to an oxygen-absorbing compositioncomprising in relatively sufficient proportions particulate annealedelectrolytically reduced iron, salt for combining with water to producean electrolyte which combines with said iron to cause it to absorboxygen, and a water-supplying component comprising activated carbon withliquid water therein for supplying said water to said salt to producesaid electrolyte.

The present invention also relates to an oxygen-absorbing packet forabsorbing oxygen in dry environments comprising the above composition inan envelope consisting of a laminate of ethylene vinyl acetate, waterand grease resistant paper, and microperforated polyester film.

The various aspects of the present invention will be more fullyunderstood when the following portions of the specification are read inconjunction with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an oxygen-absorbing packet of thepresent invention;

FIG. 2 is a cross sectional view taken substantially along line 2—2 ofFIG. 1;

FIG. 3 is a cross sectional view taken substantially along line 3—3 ofFIG. 1;

FIG. 4 is a plan view of a packet which utilizes a preferred materialfor the envelope;

FIG. 5 is an enlarged cross sectional view taken substantially alongline 5—5 of FIG. 4 and showing the material which is utilized to formthe envelope of the oxygen-absorbing packet;

FIG. 6 is a fragmentary cross sectional view taken substantially alongline 6—6 of FIG. 4;

FIG. 7 is a fragmentary cross sectional view taken substantially alongline 7—7 of FIG. 4; and

FIG. 8 is a fragmentary cross sectional view taken substantially alongline 8—8 of FIG. 4 and showing the structure of the seams.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The improved oxygen absorber, in various forms, is intended for use withvarious types of food products and other products packaged in dryenvironments, packaged in moist environments, and also products whichrequire refrigeration at temperatures below the ambient temperature andgenerally at temperatures below about 50° F. and more specifically belowabout 40° F. The improved oxygen absorber comprising annealedelectrolytically reduced iron is more efficient at both low temperaturesand normal ambient temperatures than conventional oxygen absorbers, suchas particulate electrolytically reduced iron which has not beenannealed. In this respect, it is believed that the annealing changes thestructure of the electrolytically reduced iron by inceasing the surfacearea which, in turn, causes it to be more active in its oxygen-absorbingcapacity.

The improved oxygen absorber composition of the present invention in itsmost basic form comprises particulate annealed electrolytically reducediron plus a salt which combines with moisture obtained frommoisture-impregnated activated carbon to produce an electrolyte foractivating the iron to absorb oxygen. This composition is desired foruse in dry environments. The improved oxygen-absorber composition ispreferably packaged in an envelope, described hereafter, which inhibitsmigration of moisture out of the envelope, thereby conserving suchmoisture for the oxygen-absorbing reaction.

One embodiment of a packet 10 which comprises the improved oxygenabsorber is shown in FIGS. 1-3. The packet 10 of this embodimentincludes an envelope 11 of spun-bonded polyolefin which is known underthe trademark TYVEK, and this envelope is used primarily in moistenvironments with or without silica gel as part of the oxygen-absorbingcomposition. In a moist environment the silica gel adsorbs moisture fromthe moist environment and supplies it to the remainder of the oxygenabsorbing composition, as discussed in greater detail hereafter.Envelope 10 is formed by folding flexible planar material into tubularform and fusing it along overlapping edge portions 13 and 15 to providea seam 12. The end portion is then fused at 14, as by heat and pressure,and the envelope is then filled with oxygen-absorbing material describedhereafter. Thereafter, the other end portion is fused at 18, as by heatand pressure to close the envelope. The ends of seam 12 are secured toend portion 18 at 20. This envelope structure is generally described inU.S. Pat. No. 4,992,410, which is incorporated herein by reference.However, it will be appreciated that other suitable envelopeconstructions may be use, and a preferred envelope material, which is tobe used in dry environments for an oxygen-absorbing compositioncontaining water-impregnated activated carbon is described at anappropriate point hereafter.

The particulate annealed electrolytically reduced iron which is used inthe oxygen-absorbing composition 16 can be of a size of between about 50mesh and 325 mesh and more preferably between about 100 mesh and 325mesh and most preferably about 200 mesh. It has been found that thelarger the mesh size, the slower will be the reaction. Thus, 100 meshwill react more slowly than 200 mesh which will react more slowly than325 mesh. However, the 325 mesh size is difficult to handle with certainpackaging machinery. Particulate annealed electrolytically reduced ironof various sizes which have been used are manufactured by the SCMCorporation under the designations A-210 (100 mesh), A-220 (200 mesh)and A-230 (325 mesh).

Another component of the oxygen-absorbing composition is a salt which,when combining with water, will form an electrolyte to activate theparticulate iron. The salt is preferably sodium chloride which may bepresent by weight in an amount of between about 0.4% to 3.5% andpreferably between about 1.0% and 2.0%. The salt should be present in anamount so that it is sufficiently concentrated relative to the iron sothat all portions of the iron are in contact with the electrolyte whichis formed by the salt. Above 3.5% no increase in reaction rate occurs.The exact amount of sodium chloride is not critical. The salt can bebetween about 48 mesh and 325 mesh. It will be appreciated that if anexcessive amount of iron is used for a particular environment, theamount of salt could be less than 0.4% by weight, and thus there will beoxygen absorption at a good rate, but the system will be inefficient.Therefore, it will be appreciated that the only requirement, ifefficiency is not a factor to be considered, is that the particulateannealed electrolytically reduced iron and the salt should be present insufficiently relative proportions to absorb oxygen at a desired rate.

Other equivalent salts may be substituted for the sodium choride, andthese include, without limitation, calcium chloride, potassium chloride,magnesium sulfate, magnesium chloride, barium chloride, potassiumnitrate, potassium phosphate, potassium hypophosphate, sodium carbonateand potassium carbonate. However, sodium chloride, potassium iodide,potassium bromide, calcium chloride and magnesium chloride arepreferred.

The composition of particulate annealed electrolytically reduced ironand salt, without more, provides effective oxygen absorption inatmospheres or containers wherein there is sufficient moisture tocombine with the salt to produce an electrolyte. However, inenvironments wherein there is moisture present but the amount ofmoisture is relatively low, that is, where the amount of moisture isless than that which will activate the electrolyte without the use of anagent to attract moisture, a water-attracting and supplying componentcan be added to the particulate annealed electrolytically reduced ironand salt. The water-attracting and supplying component can be a silicagel which has a water-attracting and supplying capacity. The silica gelmay be present by weight in any amount up to about 80% and morepreferably between about 40% and 50%. The water content of the silicagel by weight can vary from 0% to 32% and more preferably between about18% and 26%.

When the water-attracting and supplying component is used, the salt canbe added to both the silica gel and to the iron prior to combining them.The salt can be added to the silica gel by dissolving it in water beforebeing added to the silica gel. The silica gel can have a mesh size ofbetween about 30 mesh and 325 mesh. However, the mesh size is notcritical. Other water-attracting and supplying components may be usedand these include without limitation diatomaceous earth, perlite,zeolite, activated carbon, sand, salt, activated clay, molecular sieve,cellulose, acrylic polymers or other natural and synthetic polymers.

Of the above water-attracting and supplying components, it has beenfound that activated carbon with liquid water impregnated therein issuperior to silica gel for operation in dry environments which cannotsupply sufficient moisture for combining with the electrolyte toactivate the oxygen absorbing capability of the iron. Thewater-impregnated activated carbon is primarily a moisture supplier inthe sense that it readily gives up its impregnated water in dryenvironments whereas silica gel must generally first adsorb moisturefrom the environment before it gives it up, especially when the amountof moisture it contains is less than its saturated amount. Thus in verydry environments, the silica gel cannot effectively adsorb and supplymoisture because there is insufficient moisture for it to adsorb andthereafter release. The dry environments are those which do not havemoisture, such as canned or packaged products of various types includingbut not limited to nuts, fried foods, potato chips, cereals, grains,pharmaceuticals, powders and other materials which are subject todeterioration by oxygen but which cannot supply the moisture forcombining with the salt to produce an electrolyte. The activated carbonis especially advantageous (1) because it can have added to it arelatively large amount of water before it is placed in the dryenvironment which it will thereafter readily release after having beenplaced in the dry environment, and (2) because of its flowability as apowder after it has relatively large amounts of water added thereto andadsorbed therein, and is thus desirable from a manufacturing viewpointbecause it flows well into the envelopes both by itself and when in amixture with the particulate iron. This is in contrast to silica gelwhich becomes a slurry when it has more than 26% by weight of thecombined silica gel and moisture, and as such is not flowable. Theflowable activated carbon will not only carry the liquid water but itwill readily give it up to the salt for forming the electrolyte. This isin contrast to silica gel discussed above because the silica gel is botha water-attracting and supplying material. In this respect, the silicagel will attract water from its environment until it becomes saturatedand after it becomes saturated, it will continue to attract water untilit becomes supersaturated and then it will release the water to theenvironment. However, if there is no water in the environmentoriginally, the silica gel will be incapable of supplying liquid waterto the electrolyte because there is insufficient water in the dryenvironment to be attracted by the silica gel before it can be released.

The moisture-impregnated activated carbon, that is, the activated carbonplus its moisture, may be present in an amount of between 37% and 85% byweight of the total weight of the oxygen-absorbing composition and morepreferably between 59% and 78% and most preferably between 64% and 75%.Thus, the annealed electrolytically reduced iron can be present byweight in an amount of between about 15% and 63%, and more preferablybetween about 22% and 41%, and most preferably between about 25% and36%, and the salt can be present as noted above in an amount by weightof the iron of between about 0.4% and 3.5%. The exact amount is notcritical, and exceeding 3.5% will not hasten the reaction. The preferredsize of the activated carbon is about 20×50 mesh. However, it can rangebetween about 100 mesh to between about 4×6 mesh and it can be as smallas about 200 mesh. Also, the activity test number may be between about30 and 90 weight percent adsorption, and more preferably between about40 and 80 weight percent adsorption and most preferably between about 50and 60 weight percent adsorption; the surface area may be between about400 and 2000 sq. m/gm, and more preferably between about 600 and 1500sq. m/gm and most preferably between about 900 and 1000 sq. m/gm; thepore volume may be between about 0.3 and 1.3 cc/gm, and more preferablybetween about 0.5 and 1.0 cc/gm, and most preferably between about 0.7and 0.8 cc/gm; and the density may be between about 19 and 35 lbs/cubicfoot dry and 35 and 50 lbs/cubic foot wet, and more preferably betweenabout 25 and 34 lbs/cubic foot dry and 40 and 50 lbs/cubic foot wet, andmost preferably between about 30 and 32 lbs/cubic foot dry and 45-50lbs/cubic foot wet.

A preferred activated carbon which has been used in all of the examplesset forth hereafter has the following characteristics. It has a size of20×50 mesh; an activity of 50 to 60 weight percent adsorption; a surfacearea of 900-1000 sq. m/gm; moisture in the amount of 31-34% by weight; apore volume of 0.7 to 0.8 cc/gm; and a density of 30 to 32 lbs/ft³ dryand 45 to 50 lbs/ft³ wet.

As noted above, water is added to the activated carbon by merely mixingit therewith. The water may be present by weight as a percent of thecombined weight of the activated carbon and water between 10% and 40%and more preferably between 20% and 38% and most preferably between 31%and 35%. With all of the above percentages, the activated carbon remainsflowable as a powder, whereas when silica gel has more than 26% byweight of moisture, it becomes a slurry.

The improved composition containing annealed electrolytically reducediron, salt and activated carbon impregnated with liquid water can beprepared in the following manner. The required amount of salt, such assodium chloride, is dissolved in the required amount of water which isthereafter mixed into the activated carbon. Thereafter, the activatedcarbon with the salt water electrolyte therein is mixed or blended withthe annealed electrolytically reduced iron and the resulting compositionis placed into the envelope in which it is used. As noted above, thismixture flows well. Alternatively, the mixture of activated carbon withsalt solution therein and the annealed electrolytically reduced iron caneach be deposited separately into the envelope. As a furtheralternative, and preferably, the required amount of dry salt can bemixed with the annealed electrolytically reduced iron, and the requiredamount of water can be mixed or blended with the activated carbon, andthereafter each mixture can be independently deposited into theenvelope, or the two mixtures can be mixed with each other andthereafter deposited into the envelope.

A preferred formulation for absorbing 100 cc of oxygen consists of 200mesh annealed electrolytic iron in the amount of 0.85 grams and theabove-described preferred impregnated activated carbon in the amount of2.0 grams with the impregnated activated carbon consisting by weight of65.5% of activated carbon, 33% of water and 1.5% of sodium chloride.This 2.85 gram mixture comprises 30% by weight of iron and 70% by weightof impregnated activated carbon.

The improved oxygen absorber containing moisture-impregnated activatedcarbon for use in dry environments is packaged in a moisture and oxygenpermeable envelope which will permit oxygen to pass therethrough butwill resist the migration of the water therefrom so that such water isconfined to combining with the salt rather than being drawn away intothe dry environment, which essentially produces a desiccating action.The envelope containing the oxygen-absorbing composition comprises apacket which is placed in various types of containers including bags,cans and jars which contain materials in a dry environment.

The preferred material from which an envelope 25 is fabricated is shownin FIG. 5 and an envelope fabricated therefrom is shown in FIG. 4. Thematerial is a laminate 27 consisting of an inner layer 17 of EVA(ethylene vinyl acetate) 30 microns thick which has 250,000 holes persquare meter; a layer of water and grease resistant paper 19 having aweight of 50 grams per square meter; a layer 22 of low densitypolyethylene 15 microns thick; and an outer layer 21 of microperforatedpolyester film 12 microns thick having 13,888 holes per square meter. Itwill be appreciated that the foregoing dimensions may vary. Layer 19 ofwater and grease resistant paper limits migration of material into andout of the envelope 11 and prevents staining thereof from food on theoutside and rust from oxidation of the iron inside the envelope 11.Layer 22 of low density polyethylene is a seal layer to seal layers 19and 21 to each other, and thus the low density polyethylene layer is notconsidered part of the functioning laminate other than as a seal. Innerlayer 17 is sealed to paper layer 19. The perforated polyester outerlayer 21 is the material which contacts food or other substances withina container into which packet 10 is placed. The layers 17, 19, 22 and 21are sealed into the laminate 27 by suitable heat and pressure. The watervapor transmission rate of the laminate 27 is 50-75 grams per squaremeter per 24 hours. This is in contrast to the TYVEK which is used inmoist environments and which has a much greater vapor transmission rate.The laminate 27 is essentially a trilaminate of the EVA inner layer 17,the water and grease resistant paper 19, and the outer polyester layer21, and in the various examples presented hereafter it is referred to asa trilaminate. This trilaminate is a commercially available productknown as San-ai TJ-2802.

The foregoing laminate is especially desirable for the intended purposeof limiting or impeding migration of water out of the envelope. Theenvelope will tend to retain the water therein while permitting oxygento pass therethrough. Thus, the envelope will resist loss of water fromthe moisture-impregnated activated carbon during the packaging processand during short periods of storage so that it will be present forcombining with the salt to produce an electrolyte after it is placed ina dry environment.

The envelope 25 which is fabricated from laminate 27 is shown in FIGS.4, 6 and 7. The envelope 25 is fabricated from a folded-over piece ofmaterial 27 at fold 29, and the inner layer 17 is sealed to itself byheat and pressure to form seams 30, 31 and 32. The oxygen-absorbingcomposition 16 is placed within envelope 25 prior to sealing the last ofseams 30, 31 or 32.

The oxygen absorber composition utilizing annealed electrolyticallyreduced iron can be made into a label utilizing any of the foregoingenvelope materials which can be adhesively secured to the inside of awrapper or a container. The oxygen absorber will thus absorb oxygen fromany air which is trapped within the package or container after it hasbeen hermetically sealed, and it will also attract oxygen which mayoriginally exist within the product itself which is within the package.

The oxygen absorber containing moisture-impregnated activated carbon isintended to be used with all types of dry packaged products which may bedeleteriously affected by the presence of oxygen, and it can also beused in moist environments. These products especially comprise dryfoods, such as pasta, nuts, dried foods, prepared cereals, grains,pharmaceuticals and other dry substances, and the products also include,without limitation, non-dry foods such as meat, fish or anything elsewhich will be affected in taste or quality by the presence of oxygen.

As noted above, the improved oxygen absorber which includes particulateannealed electrolytically reduced iron is especially beneficial atrefrigerated temperatures, that is, all temperatures below about 50° F.and more preferably between about 32° F. and 40° F. It is alsobeneficial as low as 28° F., and it is believed to be beneficial attemperatures below 28° F. Stated more broadly, the improved oxygenabsorber containing annealed electrolytically reduced iron is intendedfor use especially at any refrigerated temperature which is below thenormal ambient temperature. As noted above, the oxygen absorbercontaining the particulate annealed electrolytically reduced iron isalso more effective at ambient temperatures than such a product whichhas not been annealed or other types of particulate iron which haveheretofore been used for oxygen absorption.

Various compositions have been formulated utilizing particulate annealedelectrolytically reduced iron. The following Examples 1-3 show theoxygen-absorbing capability of the annealed electrolytically reducediron in compositions which are used in moist environments and which donot include activated carbon with liquid water therein and which arepackaged in TYVEK (spun bonded polyolefin) envelopes and contain silicagel. In the moist environments the silica gel attracts water to thecomposition for activating oxygen absorption. In moist environments theTYVEK envelope is desired over the trilaminate envelope because it has ahigher water vapor transmission rate and thus can permit the silica agelto relatively rapidly receive its moisture from the moist environment.

EXAMPLE 1

A composition was prepared by mixing 0.5 grams of 200 mesh annealedelectrolytically reduced iron with 0.5 grams of 100 mesh annealedelectrolytically reduced iron. Both types of iron were previouslyblended with 2% by weight of sodium chloride having a particle size ofabout 325 mesh. The foregoing composition was sealed in a TYVEK envelopewhich was placed in a 1000 cc sealed glass jar containing atmosphericair having about 20.6% oxygen. The jar also contained a piece of blotterpaper containing about one gram of water to provide moisture. The jarwas placed in a refrigerator having a temperature of 39° F. With theforegoing blend, 59 cc of oxygen were absorbed in 24 hours, and 156 ccof oxygen were absorbed in 48 hours.

EXAMPLE 2

The same formulation as set forth in Example 1 was placed in a 2-gallonplastic air-tight container having 7500 cc of atmospheric air containingabout 20.6% of oxygen, or 1559 cc of oxygen. A piece of blotter papercontaining four grams of water was also placed in the container. Thecontainer was sealed and placed in a 39° F. refrigerator. Thetheoretical capacity of the formulation containing one gram of iron is295 cc of oxygen. At refrigerated conditions of 39° F., the aboveformulation absorbed 20% of its theoretical capacity of 295 cc ofoxygen, or 59 cc, in 24 hours and a total of 53%, or 156 cc, theoreticalcapacity of 295 cc in 48 hours.

EXAMPLE 3

A mixture was provided in a TYVEK packet containing 0.5 grams of 200mesh annealed electrolytically reduced iron, 0.5 grams of 100 meshannealed electrolytically reduced iron, and 0.8 grams hydrated silicagel containing 21% moisture. The composition also contained 1.5% byweight of sodium chloride having a mesh size of 325. The hydrated silicagel had a mesh size of between 30 and 200. The above formulation wasplaced in a TYVEK envelope, and the sealed envelope was inserted into a1000 cc glass jar containing atmospheric air containing about 206 cc ofoxygen which was then sealed and placed in a refrigerator having atemperature of 39° F. The foregoing formulation absorbed 35% of itstheoretical capacity of 295 cc of oxygen in 24 hours, and it absorbed58% of its theoretical capacity of 295 cc of oxygen in 48 hours. Thus,it absorbed 103 cc of oxygen in 24 hours and 171 cc in 48 hours. It canthus be seen that Example 3 which contains the hydrated silica gel ismuch faster acting in the first 24 hours than the composition of Example1 which contains the same amounts of 100 mesh and 200 mesh iron but doesnot contain the silica gel.

Comparisons were made of the oxygen-absorbing characteristics of likecompositions of both annealed electrolytically reduced iron andnon-annealed electrolytically reduced iron, and it was found that theformer absorbed oxygen at a much faster rate. More specifically, twocompositions were made. Composition A contained 0.85 grams of 200 meshannealed electrolytically reduced iron and 1.36 grams of silica gelcontaining 23% water and 1.5% sodium chloride. Composition B had thesame ingredients, except that the iron was electrolytically reduced, butnot annealed. Each composition, after blending, was placed in a TYVEKenvelope and each was then placed in a separate air-tight glasscontainer having about 500 cc of atmospheric air which included about100 cc of oxygen. The containers each also had a piece of blotter paperplaced therein containing one gram of water. Each container was thenplaced in a 38° F. refrigerator. The following rates of oxygenabsorption were observed:

AMOUNTS OF OXYGEN ABSORBED IN CC Elapsed time Composition A CompositionB in hours (Annealed) (Non-annealed) 19  91 29 25 100 60 28 — 71 42 —100 

It was also found that the reaction temperatures utilizing annealedelectrolytically reduced iron at ambient temperatures was much fasterthan the use of electrolytically reduced iron which was not annealed.

Tests were made of the rate of oxygen absorption of a mixture containingannealed electrolytically reduced iron at room temperature of about 72°F. A mixture containing 0.85 grams of A-220 annealed electrolyticallyreduced iron of 200 mesh with 1.36 grams of silica gel containing 26%water and 1.5% sodium chloride was placed in a TYVEK envelope which wassealed. The packet consisting of the sealed envelope and its contentswas placed in a 500 cc glass jar containing a gram of water on blotterpaper. The jar contained 500 cc of atmospheric air containing about 100cc of oxygen. Three jars were tested with one packet in each jar, andthe average of three tests showed that after 2 hours 19 cc of oxygenwere absorbed, after 4 hours 73 cc were absorbed, and at 6 hours 100 ccwere absorbed. Tests were also made under substantially identicalconditions with the only change being the use of non-annealed reducediron. As a result of such tests, it was found that after 2 hours 7 cc ofoxygen was absorbed, after 4 hours 10 cc was absorbed, after 7 hours 29cc was absorbed and after 24 hours 100 cc was absorbed. The above datais set forth in the following table for ease of comparison:

COMPARISON OF OXYGEN ABSORPTION RATES IN CC Time in Hours Composition 24 6 7 A 19 73 100 — B  7 10 — 29

where A is annealed electrolytically reduced iron and B is non-annealedelectrolytically reduced iron.

The following Examples 4-7 are directed to the use of water-impregnatedactivated carbon in dry environments and show the differences in resultswhich were obtained by using TYVEK envelopes versus trilaminateenvelopes. The results of the TYVEK envelopes are set forth in Examples4 and 6, and the results of the trilaminate envelopes are set forth inExamples 5 and 7. Example 4 is to be compared with Example 5 and Example6 is to be compared with Example 7.

EXAMPLE 4

A composition was prepared by blending 0.34 grams of 100 mesh annealedelectrolytically reduced iron with water-impregnated activated carbon ofthe above-described preferred type in the amount of 0.90 grams exceptthat it contained 35% by weight of water and 1.5% by weight of sodiumchloride. The impregnated activated carbon was of 20×50 mesh andconsisted of 0.57 grams of activated carbon and 0.31 grams of water and0.014 grams of sodium chloride. Thus, the water consisted of 35% of thetotal weight of the impregnated activated carbon. The total weight ofthe mixture of iron activated carbon, salt and water was 1.24 grams. Themixture was placed in a TYVEK envelope, Grade 1059B, and the envelopecontaining the mixture was placed in a 500 cc jar containing 25 grams ofdry prepared breakfast cereal, LUCKY CHARMS brand, which occupied about160 milliters of space. The jar was maintained at an ambient temperatureof about 70° F. The following test results were obtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 19 2.1cc 25 2.4 cc 42 2.2 cc

EXAMPLE 5

A test was made which was identical to Example 4 except that theenvelopes were made of the trilaminate film described above, and thefollowing results were obtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 19 25.7cc 25 27.4 cc 42 27.4 cc

EXAMPLE 6

A test was made which was identical to Example 4 except that 0.80 gramsof the above-described preferred impregnated activated carbon was usedcontaining by weight 33% water and 1.5% sodium chloride. Thus the samplecontained 0.52 grams of activated carbon, 0.26 grams of water and 0.012grams of salt. A TYVEK envelope was used. The results were as follow:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 19 4.0cc 25 4.7 cc 42 4.7 cc

EXAMPLE 7

A test was made which was identical to Example 6 except that theenvelopes were made of trilaminate film described above, and thefollowing results were obtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 19 50.4cc 25 55.4 cc 42 57.4 cc

An analysis of Examples 4-7 reveals that the combination of impregnatedactivated carbon in a trilaminate envelope produces much better oxygenabsorption than the combination of the same amounts of impregnatedcarbon in a TYVEK envelope. In this respect, a comparison of Examples 4and 5 wherein the impregnated activated carbon had 35% water, the oxygenabsorption was much greater in a trilaminate envelope. A comparison ofExamples 6 and 7 shows similar results to Examples 4 and 5, namely, thatthe impregnated activated carbon in the trilaminate envelope absorbed anaverage of about 54.3 cc versus about an average of 4.5 cc for the TYVEKenvelope. The differences favoring the use of impregnated activatedcarbon in a trilaminate envelope over a TYVEK envelope is that thetrilaminate will impede the migration of water out of the envelopewhereas the TYVEK does not impede this migration because it has a higherwater vapor transmission rate. In the present instance the dry cerealacted as a desiccant to draw the moisture out of the TYVEK envelope at amore rapid rate than from the trilaminate, that is, before the moisturecan work with the salt to produce sufficient electrolyte for activatingthe iron. Stated otherwise, the trilaminate, by impeding the passage ofmoisture without impreding the passage of oxygen permits the activatedcarbon to release its moisture to the salt to create the electrolyte toactivate the iron to combine with and thus absorb the oxygen.

The following tests set forth in Examples 8-15 were also made to showthat silica gel in a trilaminate envelope does not work as effectivelyas impregnated activated carbon in a trilaminate envelope even if itpossesses the same total amount of water as impregnated activatedcarbon. In these examples the silica gel only contained 21% by weight ofwater, which is substantially the maximum amount it can have and stillremain flowable. In these tests, while the silica gel had only 21% wateras compared to the 35% water of the activated carbon, the amount ofsilica gel was increased so that the total amount of water in the silicagel was equal to the total amount of water in the impregnated activatedcarbon.

EXAMPLE 8

A composition was prepared by blending 0.33 grams of 100 mesh annealedelectrolytically reduced iron with 0.01 grams of 325 mesh sodiumchloride to provide a total weight of 0.34 grams with the sodiumchloride comprising 2% of the weight of the iron. Water-impregnatedactivated carbon of the above-described preferred type except as notedhereafter in the amount of 0.61 grams was blended with the mixture ofiron and sodium chloride. The impregnated activated carbon was of 30×80mesh and consisted of 0.40 grams of activated carbon and 0.21 grams ofwater. Thus, the water consisted of 35% of the total weight of theimpregnated activated carbon. The total weight of the mixture of ironactivated carbon, salt and water was 0.95 grams. The mixture was placedin a trilaminate envelope, and the envelope containing the mixture wasplaced in a 500 cc jar containing air. The jar was maintained at anambient temperature of about 70° F. The following test results wereobtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 17 13cc 24 16 cc 41 31 cc

EXAMPLE 9

Tests were performed which were identical to Example 8 except that 1.00grams of silica gel containing 21% by weight of water was substitutedfor the 0.61 grams of impregnated activated carbon containing 35% byweight of water so that the total water contents of the silica gel andthe activated carbon were equal, and the following results wereobtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 19 0 250 42 0

EXAMPLE 10

Tests were performed which were identical to Example 8 except that 0.61grams of impregnated activated carbon of the above preferred type wasused except that it contained 28% by weight of water, i.e., 0.17 gramsof water, and the following results were obtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 17 16cc 24 22 cc 41 29 cc

EXAMPLE 11

Tests were performed which were identical to Example 10 except that 0.81grams of silica gel containing 21% by weight of water was substitutedfor the activated carbon, i.e., 0.17 grams of water and the followingresults were obtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 19 0 cc25 0 cc 42 0 cc

EXAMPLE 12

Tests were performed which were identical to Example 8 except that 0.90grams of 20×50 mesh of the above-described preferred impregnatedactivated carbon containing 33% by weight of water and containing 1.5%by weight of NaCl was used, and the 0.34 grams of iron did not have NaCladded thereto. Thus this composition contained 0.31 grams of water. Thefollowing results were obtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 24 31cc 44 41 cc 89 51 cc

EXAMPLE 13

Tests were performed which were identical to Example 12 except that 1.5grams of silica gel containing 21% water plus 1.5% sodium chloride wassubstituted for the activated carbon. Thus the water content was 0.31grams. The following results were obtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 19 0 cc25 0 cc 42 0 cc

EXAMPLE 14

Tests were performed which were identical to Example 8 except that 0.80grams of 20×50 mesh of the above-described preferred impregnatedactivated carbon was used which contained by weight 33% water plus 1.5%NaCl. This amounted to 0.26 grams of water. The following results wereobtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 24 67cc 44 79 cc 89 90 cc

EXAMPLE 15

Tests were performed which were identical to Example 14 except itsubstituted for the activated carbon 1.25 grams of silica gel containingby weight 21% water and 1.5% NaCl. This amounted to 0.26 grams of water.The following results were obtained:

Average Oxygen Elapsed Time Absorption of in Hours Three Samples 19 0 cc25 0 cc 42 0 cc

A comparison of Examples 8 and 9; 10 and 11; 12 and 13; and 14 and 15shows that even when flowable silica gel having 21% of water is used insufficient amounts to provide total amounts of water which are equal tothe total amounts of water contained in moisture-impregnated activatedcarbon, the oxygen absorption produced by the impregnated activatedcarbon greatly exceeds the oxygen absorption of the silica gel. In fact,as can be seen from Examples 9, 11, 13 and 15, there was no oxygenabsorption in a dry environment by the silica gel because it does notgive up its water to produce the necessary electrolyte, whereas inExamples 8, 10, 12 and 14 the activated carbon does give up its waterfor combining with the salt to form an electrolyte.

Summarizing, the moisture-impregnated activated carbon containing arelatively large amount of water is flowable, and it readily gives upthis water in dry environments. Additionally, when such impregnatedactivated carbon is used in the above-described trilaminate envelope,the latter impedes the migration of water out of the envelope, and thusconserves it for combining with the salt of an oxygen-absorbingcomposition. On the other hand, the silica gel is preferred for use inmoist environments because of its great water-attracting capacity, and,further, the TYVEK is preferable in a moist atmosphere because it has agreater water vapor transmission rate than the trilaminate.

Generally the finer the particulate iron which is used, the speedierwill be the oxygen absorption. Thus, 325 mesh iron and above ispreferred from a theoretical viewpoint. However, the fineness may belimited by the use of the machinery which is utilized to fabricate thepackets or labels discussed above.

While preferred embodiments of the present invention have beendisclosed, it will be appreciated that the present invention is notlimited thereto but may be otherwise embodied within the scope of thefollowing claims.

What is claimed is:
 1. A packet for absorbing oxygen comprising an oxygen-absorbing composition including in relatively sufficient proportions particulate annealed electrolytically reduced iron, salt for combining with water to produce an electrolyte which combines with said iron to cause it to absorb oxygen, and an envelope enclosing said composition which inhibits migration of water from said envelope.
 2. A packet for absorbing oxygen comprising an oxygen-absorbing composition including in relatively sufficient proportions particulate annealed electrolytically reduced iron, salt for combining with water to produce an electrolyte which combines with said iron to cause it to absorb oxygen, and a moisture and oxygen permeable envelope containing said composition and which permits oxygen to pass therethrough but resists the migration of water therefrom.
 3. A packet for absorbing oxygen comprising an oxygen-absorbing composition including in relatively sufficient proportions particulate annealed electrolytically reduced iron, salt for combining with water to produce an electrolyte which combines with said iron to cause it to absorb oxygen, and an envelope containing said composition which permits oxygen to pass therethrough while tending to retain water therein.
 4. A packet as set forth in claim 1 wherein said oxygen-absorbing composition includes activated carbon with liquid water therein for supplying said water to said salt to produce said electrolyte.
 5. A packet as set forth in claim 4 wherein said water-supplying component is present by weight in an amount of up to about 85% of the total weight of the oxygen-absorbing composition.
 6. A packet as set forth in claim 5 wherein said water-supplying component contains by weight up to about 40% of water.
 7. A packet as set forth in claim 2 wherein said oxygen-absorbing composition includes activated carbon with liquid water therein for supplying said water to said salt to produce said electrolyte.
 8. A packet as set forth in claim 7 wherein said water-supplying component is present by weight in an amount of up to about 85% of the total weight of the oxygen-absorbing composition.
 9. A packet as set forth in claim 8 wherein said water-supplying component contains by weight up to about 40% of water.
 10. A packet as set forth in claim 3 wherein said oxygen-absorbing composition includes activated carbon with liquid water therein for supplying said water to said salt to produce said electrolyte.
 11. A packet as set forth in claim 10 wherein said water-supplying component is present by weight in an amount of up to about 85% of the total weight of the oxygen-absorbing composition.
 12. A packet as set forth in claim 11 wherein said water-supplying component contains by weight up to about 40% of water. 